Blackboards in Porn

I appreciated this generous interpretation of a blackboard reading "1+1=2":

> This is clearly an extremely advanced level mathematical course, focusing on the Peano axioms for the natural numbers which formalised mathematics in the late 19th century. This course would culminate with Gödel's second incompleteness theorem which shows that the consitency of the Peano axioms cannot be formalised within Peano arithmetic itself.

>(Why the teacher has chosen A and S is unclear; these are sometimes used in lower case form as acceleration and distance respectively, but the relationship between them would not then be physically correct.)

A and S are used in elementary math as Area and Side respectively, so for a square it is correct.